Which one is the definition of Use Case?

You need to test a vending machine for light drinks. The machine has a button for each of the drinks it contains.
Pressing a button before inserting coins, will display the cost of the drink. Pressing the same button after inserting enough coins will dispense the drink and provide change if needed).
If the machine is out of the specific drink, and the button for this drink is pressed, the machine displays "Sold Out" (regardless if coins were inserted or not).
Which test technique is most suitable for this situation?

The development manager is managing the review of the responses received from bidders, and has asked the in-house test manager to provide a review checklist for the test management aspects of the responses. Which of the following checkpoints would be appropriate?

What is the purpose of test completion criteria in a test plan:

Which of the following would be the TWO most appropriate examples of entry criteria documented in the system integration test plan?